of salt lake city



Feb. 3, 1931. D. R. SEELY ACOUSTIC DIAPHRAGM AND MOUNTING Filed Aug. 20,1928 HIZ INVOR 0 l .0. E. 55152 7 BY ATTORNEY non a. SEELY, or sam" 1m01in, uumassmnon 'ro THE um: mio raonuc'rs' Patented Feb. 3, 1931 UNITEDSTATES, PATENT OFFICE COMPANY, OF SALT LAKE CITY, UTAH, A CORPORATION OFACOUSTIC DIAPHRAGM AN D MOUNTING Application filed August 20, 1928.Serial No. 300,748.

" or reproducing sounds having frequencies extending over a wide range.

Second. One which shall give forth rich mellow tones.

Third. A wooden diaphragm which shall -be stron durable, andmoisture-resistant,

and thus e suited to varying climatic conditions.

In the quest of an improved material for diaphragms, particularly of thekind used for radio loud speakers, I have found that wood has propertieswhich are particularly suited to give forth rich, mellow sounds. Thewoodma be of different kinds, such as pine, spruce, irch or the like,cut into thin sheets. 7

The ratio of the thickness of a sheet of the wood, to the area of thefinished diaphragm,

' forms an important part ofthe invention. This ratio varies betweencertain limits, but

its maximum I place at one eighth of an inch per square foot of area ofthe finished diaphragm. As a rule, however, this ratio may beconsiderably less.

, The superficial shape of the diaphragm may be round, square,elliptical, oblong or otherwise, so long as the conditions for propervibratory motion are maintained.

1 ,Thin, sheets of wood when first formed, give quite satisfactoryresults when used as diaphragms, butvery soon, the contraction, due tothe seasoning manifested when freshly cut wood fibers are exposed to theatmosphere, cause objectionable cracks and checks to appear, which ofcourse impair the desirable properties of the wood, and soon render theuntreated wood diaphragm unfit for service. I V

The treatment accorded the wood sheets, by means of the presentinvention, gives a high degree 'of permanence to the desirable acousticproperties originally possessed by the wooden sheets, and preservestheir capability to give forththe peculiarly rich and mellow toneswhich-may originally emanate therefrom. My aim is to interfere as littlesheets such structural support, strength and toughness, as shall insuretheir durability. In many cases, my treatment improves the naturalacoustic properties of the wood.

To this end, the sheets of wood are, impregnated with a nitrocellulosesolution, for instance, ambroid, whichafter the evaporation of thevolatile constituents thereof, leaves the resinous fibers of. the woodcemented together. This cementing is effected by the tough, flexible andwaterproof residue permeating the pith of the wood after the saidevaporation. The wood, further, may be covered with a textile fabric,for example, cambric, whose threads in the war and woof are preferablyplaced substantial y diagonal with the grain of the wood. The cloth maybe cemented or glued to the wood, and both the wood and the clothimpregnated with the nitrocellulose solution.

If desired, the wood may be first impregnated with the nitrocellulosesolution, and the cloth be cemented thereto by laying the cloth on thewood and applying a coat of the said solution. After the application ofthe nitrocellulose solutionthe sheets may be subjected to suitablepressure, applied by means of presses similar to those used in theordinary laminating of wood for panelsand the like. If .foundadvantageous, the cloth ma'g be applied to the wood sheets in strips orribbons rather than in continuous layers, these strips being appliedeither to one or both surfaces of the wood', and running in onedirection on one side of the sheet, and in the transverse direction onthe other side of the sheet, or the strips may be criss-icr'ossed in twoseries, one series being on each surface.

In use, the diaphragm may be supported by a wooden frame conforming tothe superficial shape of the diaphragm, said frame having a depthtransverse to the surface ofthe diaphragm sufficient to insure;rigidity, and also to form a cabinet or other structure for concealingthe loud speaker actuating unit, which latter maybe of any desired typein ordinary use.

I The features of this invention for which the protection of LettersPatent of the United States is desired, are collectively grouped in theclaims concluding this specification.

In the drawing, which illustrates merely one embodiment of thisinvention,

Fig. 1 represents a rear elevation of a loud speaker whose "equipmentincludes my improved diaphragm and itsmounting;

Fig. 2, a section on line 2, Fig. 1, V v

Fig. 3, a rear elevation, parts being omitted;

Fig. 4-,aminor detail; i.

Figs. 5 and 6, fragmentary elevations showing variations in thestructural constitution ofv the diaphragm proper Fig. 5 being a frontelevation and Fig. 6 a rear elevation reflected from a mirror plane; and

Fig. 7, a fragmentary cross-section in diagram, greatly enlarged, toshow the theoretical structure of this improved diaphragm.

Referring to the drawing, 10 indicates a frame of substantially squaresuperficial configuration, made up of the individual members 12, whichmay be mitered together at the corners as indicated at 14.

The diaphragm is indicated at 15, and this may be attached to one faceof the frame in any suitable manner, such as by gluing or cementing.

Either one or both of the superficial surfaces 16 and 17 of thediaphragm may be covered with a thin textilefabric such as cambric,applied diagonally with respect to the direction in which runs the grainof the wood at the faces of the diaphragm, some what after the mannerindicatedat 18 and 19 in Figs. 1 and 3, the grain of the wood beingassumed to run as indicated by the doublepointed arrow 24. The layers ofcloth, 18 and 19,.may be cemented to the wooden sheet 15 before thelatter is attached to the frame 10, and both surfaces may be treatedwith amberoid or other nitrocellulose solution, either before or afterthe diaphragm is applied to the frame 10. v 1 I t v In order to stiffenthe diaphragm and to improve its vibratory qualities,'diagonal ribs 20.of wood or other suitable material, may be attached to one face of thediaphragm, and other ribs 21 of similar material may be ap pliedtransverse to the grain of the wood of the diaphragm.

Inside of the frame 10 may beblocks 25, to which is attached thecross-piece 26, the latter being spaced apart from the diaphragm 15'sufficiently far to clear the ribs 20 and 21. On the cross-piece 26 ismounted any desired vibratory actuating unit 27, such as one of the wellknown electromagnetic push-and-v pull type. This unit may be held inplace by means of the strap 28,

Strap 28 engages the bolts 29, the latter being fastened in thebase 30,which inturn may be attached to the cross-piece- 26 by means of thescrews 31. The armature40 of diagonal to the grain of the wood, Whichisassumed to extend 1n the direction indicated by the arrows 35. It isevident that the strips 32 or 38 as the case may he, might be omitted,thus; leaving only one series of strips on each side of the diaphragm,these two. remaining series of strips however, being preferablytransverse to each other; Taking the small circle 42- as a point ofreference, it will be noted that the strips 32 and 36 alternate withstrips 34 and 38 respec-' tively, in relative positions. 7 I

The wood sheets may be single in ply, or they may be laminated so as tobe composed of two or more plies. In a multiple-ply sheet, thedirections of the grains of the individual plies would be perpendicularto each other or to one another, as the case might be, but the warp andwoof ofthe cloth, if used, would nevertheless be sub stantially diagonalto the grain of the face laminations. c,

It is to be understood that the textile fabric is not used in all cases,as the treatment of the wood with the nitrocellulose solution alone addsstrength and durability to the wood. However, in cases where stillgreater strength and durability are desired, the textile fabric isemployed. i

In Fig. 7 is indicated the structure of this improved diaphragm inaccordance withits fundamental theory. The pith 49 is saturated with thenitrocellulose solution, which latter upon evaporation of its volatileconstituents, leaves the pith permeated with the tough, solidifiedconstituents of the nitrocellulose solution. The solidified constituentsserve to flexibly cement the resinous fibers or minute'tubes bO of thewood together, thusproducing a durable material for diaphragms. Theoptionalcovering of cloth for the superficial faces ofjthe wood sheet,as hereinbefore mentioned, is indicated at 18.and 19 (Fig. 7). I

In the present instance, each side of the square inside the frame10fmight be one foot long,.in'-which casethe dimension 51 in Fig. 7would be one-eighth inch or less.

While a specific embodiment of this invention is herein shown anddescribed, it is to be clearly understood that variations within thescope of the accompanying claims,

may be resorted towithout jeopardizing my patent protection.

'Having fully; described my invention, what I claim is:

1. An acoustic diaphragm formed of a sheet of wood which has beenimpregnated with a nitrocellulose solution.

2. An acoustic diaphragm formed of a sheet of wood in which are retainedthe solidified constituents of a nitrocellulose solution.

3. An acoustic diaphragm formed of a sheet of wood which has beenimpregnated with a nitrocellulose solution, and having cloth cemented tothe superficial surface of said sheet.

4. An acoustic diaphragm formed of a sheet of wood in which are retainedthe solidified constituents of a nitrocellulose solution, and havingcloth cemented to the superficial surface of said sheet.

5. An acoustic diaphragm formed of a sheet of wood which has beenimpregnated with a nitrocellulose solution, and having cloth cemented tothe superficial surface of 'said sheet, said cloth having its warp andwoof in dia onal relation to the grain of the said wood s eet.

6. An acoustic diaphragm formed of a sheet of wood in which are retainedthe solidified constituents of a nitrocellulosesolution, and having atextile fabric cementedto the superficial surface of said sheet, saidtextile fabric having its Warp and woof in diagonal relation to thegrain of the said wood sheet.

7. An acoustic diaphragm formed of a sheet ofwood, and a layer oftextile fabric attached to the superficial surface of said wooden sheet,the warp and the Woof of the said textile fabric being substantiallydiagonal to the grain of the said wooden sheet.

8. An acoustic diaphragm composed of wood less than one-eighth inch inthickness for each square foot of superficial area of the saiddiaphragm, said wood having been impregnated with a solution ofnitrocellulose.

9. An acoustic diaphragm comprising a sheet of wood having a thicknessone-eighth inch or less for each superficial square foot of area of thesaid diaphragm, and a mass of the solidified constituents of anitrocellulose solution permeating the sheet.

10. An acoustic diaphragm comprising a sheet of wood one-eighth inch orless in thickness for each superficial square foot area thereof, and alayer of textile fabric attached to the said sheet, the warp and woof ofthe textile fabric being substantially diagonal to the grain of the saidwood.

11. An acoustic diaphragm comprising a sheet of wood, a textile fabriccemented to the face of the said sheet, the Warp and the Woof of thesaid textile fabric being substantially diagonal to the grain of thesaid Wood, and a nitrocellulose residue in a cemented relation to thesaid textile fabric and the said I wooden sheet.

12. An acoustic diaphragm comprising a sheet of wood, a nitrocelluloseresidue permeating the said wood, and a textile fabric cemented to thesurface of the said wood.

13. An acoustic diaphragm com rising a sheet of wood, layers of textileabric cemented to the face of the said sheet, the warp and the woof ofthe said textile fabric being substantially diagonal to the grain of thesaid wood, a nitrocellulose residue permeating said diaphragm, a framehaving a configuration corresponding to the contour of the saiddiaphragm, said diaphragm attached to said frame, and means for operablymounting an actuating unit within said frame in a manner such that saidunit may be connected to said diaphragm.

14. A wooden diaphragm having a thickness less than one-eighth inch forevery square foot of superficial area of said diaphragm, a frame havinga configuration corresponding .to the perimeter of said diaphragm andrigidly fastened to said frame along said perimeter, the members of saidframe being substantially transverse to the surface of said diaphragm,and having their outer surfaces flush with the edges of said diaphragm,and means for operably mounting an actuating unit for said diaphragmwithin said frame.

In testimony whereof I sign my name hereto.

DON R. SEELY.

